Phased array intravascular devices, systems, and methods utilizing photoacoustic and ultrasound techniques`

ABSTRACT

Imaging devices, systems, and methods are provided. Some embodiments of the present disclosure are particularly directed to imaging a region of interest in tissue with photoacoustic and ultrasound modalities. In some embodiments, a medical sensing system includes one or more external optical emitters and a measurement apparatus configured to be placed within a vascular pathway. The measurement apparatus may include a sensor array comprising sensors of two or more types. The sensors may be configured to receive sound waves created by the interaction between emitted optical pulses and tissue, and transmit and receive ultrasound signals. The medical sensing system may also include a processing engine operable to produce images of the region of interest and a display configured to visually display the image of the region of interest.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of Application Serial No. 16/089,037,filed Sep. 27, 2018, now U.S. Pat. No. 11,660,070, which is the U.S.National Phase application under 35 U.S.C. §371 of InternationalApplication No. PCT/EP2017/057332, filed on Mar. 28, 2017, which claimsthe benefit of Provisional Application Serial No. 62/315,220, filed Mar.30, 2016. These applications are hereby incorporated by referenceherein.

TECHNICAL FIELD

The present disclosure relates generally to imaging, in particular, toimaging a region of interest in tissue with a transducer incorporatingmultiple imaging modalities.

BACKGROUND

Innovations in diagnosing and verifying the level of success oftreatment of disease have migrated from external imaging processes tointernal diagnostic processes. In particular, diagnostic equipment andprocesses have been developed for diagnosing vasculature blockages andother vasculature disease by means of ultra-miniature sensors placedupon the distal end of a flexible measurement apparatus such as acatheter, or a guide wire used for catheterization procedures. Forexample, known medical sensing techniques include angiography,intravascular ultrasound (IVUS), forward looking IVUS (FL-IVUS),fractional flow reserve (FFR) determination, a coronary flow reserve(CFR) determination, optical coherence tomography (OCT),trans-esophageal echocardiography, and image-guided therapy.

For example, intravascular ultrasound (IVUS) imaging is widely used ininterventional cardiology as a diagnostic tool for assessing a diseasedvessel, such as an artery, within the human body to determine the needfor treatment, to guide the intervention, and/or to assess itseffectiveness. There are two general types of IVUS devices in use today:rotational and solid-state (also known as synthetic aperture phasedarray). For a typical rotational IVUS device, a single ultrasoundtransducer element is located at the tip of a flexible driveshaft thatspins inside a plastic sheath inserted into the vessel of interest. Inside-looking rotational devices, the transducer element is oriented suchthat the ultrasound beam propagates generally perpendicular to thelongitudinal axis of the device. In forward-looking rotational devices,the transducer element is pitched towards the distal tip so that theultrasound beam propagates more towards the tip (in some devices, beingemitted parallel to the longitudinal centerline). The fluid-filledsheath protects the vessel tissue from the spinning transducer anddriveshaft while permitting ultrasound signals to propagate from thetransducer into the tissue and back. As the driveshaft rotates, thetransducer is periodically excited with a high voltage pulse to emit ashort burst of ultrasound. The same transducer then listens for thereturning echoes reflected from various tissue structures. The IVUSmedical sensing system assembles a two dimensional display of thetissue, vessel, heart structure, etc. from a sequence ofpulse/acquisition cycles occurring during a single revolution of thetransducer. In order to image a length of a vessel, the transducerelement is drawn through the vessel as it spins.

In contrast, solid-state IVUS devices utilize a scanner assembly thatincludes an array of ultrasound transducers connected to a set oftransducer controllers. In side-looking and some forward-looking IVUSdevices, the transducers are distributed around the circumference of thedevice. In other forward-looking IVUS devices, the transducers are alinear array arranged at the distal tip and pitched so that theultrasound beam propagates closer to parallel with the longitudinalcenterline. The transducer controllers select transducer sets fortransmitting an ultrasound pulse and for receiving the echo signal. Bystepping through a sequence of transmit-receive sets, the solid-stateIVUS system can synthesize the effect of a mechanically scannedtransducer element but without moving parts. Since there is no rotatingmechanical element, the transducer array can be placed in direct contactwith the blood and vessel tissue with minimal risk of vessel trauma.Furthermore, because there is no rotating element, the interface issimplified. The solid-state scanner can be wired directly to the medicalsensing system with a simple electrical cable and a standard detachableelectrical connector. While the transducers of the scanner assembly donot spin, operation is similar to that of a rotational system in that,in order to image a length of a vessel, the scanner assembly is drawnthrough the vessel while stepping through the transmit-receive sets toproduce a series of radial scans.

Rotational and solid-state state IVUS are merely some examples ofimaging modalities that sample a narrow region of the environment andassemble a two- or three-dimensional image from the results. Otherexamples include optical coherence tomography (OCT), which has been usedin conjunction with ultrasound systems. One of the key challenges usingthese modalities within a vascular pathway is that they are limited ingathering data on anatomy beyond the vessel walls. Although OCT imagingmay yield higher resolution than IVUS imaging, OCT has particularlylimited penetration depth and may take more time to image a region oftissue.

Another modern biomedical imaging modality is photoacoustic imaging.Photoacoustic imaging devices deliver a short laser pulse into tissueand monitor the resulting acoustic output from the tissue. Due tovarying optical absorption throughout the tissue, pulse energy from thelaser pulse causes differential heating in the tissue. This heating andassociated expansion leads to the creation of sound waves correspondingto the optical absorption of the tissue. These sound waves can bedetected and an image of the tissue can be generated through analysis ofthe sound waves and associated vascular structures can be identified, asdescribed in U.S. Pat. Publication 2013/0046167 titled “SYSTEMS ANDMETHODS FOR IDENTIFYING VASCULAR BORDERS,” which is hereby incorporatedby reference in its entirety.

Accordingly, for these reasons and others, the need exists for improvedsystems and techniques that allow for the mapping of vascular pathwaysand surrounding tissue.

SUMMARY

Embodiments of the present disclosure provide devices, systems, andmethods that combine photoacoustic and IVUS imaging techniques. Thedevices, systems, and methods may include a sensor array that may allowfor imaging and/or mapping of vascular pathways and surrounding tissue.

In some embodiments, a medical sensing system is provided comprising: anoptical emitter configured to emit optical pulses to tissue in a regionof interest; and a measurement apparatus configured to be placed withina vascular pathway in the region of interest, wherein the measurementapparatus comprises a sensor array comprising two or more sensorelements, wherein the measurement apparatus is configured to: receivesound waves generated by the tissue as a result of interaction of theoptical pulses with the tissue; transmit ultrasound signals; and receiveultrasound echo signals based on the transmitted ultrasound signals.

In some embodiments, the sensor array is disposed circumferentiallyaround a distal portion of the measurement apparatus. The two or moresensor elements may cover equal surface area on the transducer array. Aprocessing engine may also be included which is operable to control themeasurement apparatus and the optical emitter. In some embodiments, theprocessing engine is further operable to synchronize movements of theoptical emitter and the measurement apparatus and/or operable to producean image of the region of interest based on the received sound waves andthe received ultrasound echo signals.

In some embodiments, the two or more sensor elements comprise at leastone photoacoustic transducer and at least one ultrasound transduce. Theat least one ultrasound transducer may be configured to transmitultrasound signals and receive ultrasound echo signals based on thetransmitted ultrasound signals. The at least one ultrasound transducermay be further configured to receive sound waves generated by the tissueas a result of interaction of the optical pulses with the tissue. The atleast one photoacoustic transducer may be configured to receive thesound waves generated by the tissue as a result of interaction of theoptical pulses with the tissue. In some embodiments, the at least onephotoacoustic transducer and the at least one ultrasound transducer areconfigured to alternate in receiving sound waves and ultrasound echosignals.

In some embodiments, a medical sensing system is provided comprising: anoptical emitter configured to emit optical pulses to tissue in a regionof interest; a measurement apparatus configured to be placed within avascular pathway in the region of interest, wherein the measurementapparatus comprises a sensor array comprising two or more sensorelements, wherein the measurement apparatus is configured to: receivesound waves generated by the tissue as a result of interaction of theoptical pulses with the tissue; transmit ultrasound signals; and receiveultrasound echo signals based on the transmitted ultrasound signals; aprocessing engine in communication with the measurement apparatus, theprocessing engine operable to produce an image of the region of interestbased on the received sound waves and the received ultrasound echosignals; and a display in communication with the processing engine, thedisplay configured to visually display the image of the region ofinterest.

In some embodiments, the two or more sensor elements comprise at leastone photoacoustic transducer and at least one ultrasound transducer. Theat least one ultrasound transducer may be configured to transmitultrasound signals and receive ultrasound echo signals based on thetransmitted ultrasound signals. In some embodiments, the at least oneultrasound transducer is further configured to receive sound wavesgenerated by the tissue as a result of interaction of the optical pulseswith the tissue. The at least one photoacoustic transducer may beconfigured to receive the sound waves generated by the tissue as aresult of interaction of the optical pulses with the tissue. In someembodiments, the at least one photoacoustic transducer and the at leastone ultrasound transducer are configured to alternate in receiving soundwaves and ultrasound echo signals.

In some embodiments, a method of mapping a region of interest isprovided, comprising: transmitting, with a laser source disposed outsidea body of a patient, a focused laser pulse on tissue in a region ofinterest having at least one vascular pathway; receiving, with atransducer array positioned within the vascular pathway of the region ofinterest, sound waves generated by the interaction of the focused laserpulse with the tissue; transmitting, with at least one transducer of thetransducer array, ultrasound signals toward the tissue in the region ofinterest; receiving, with the at least one transducer of the transducerarray, ultrasound echo signals of the transmitted ultrasound signals;producing an image of the region of interest based on the received soundwaves and the received ultrasound echo signals; and outputting the imageof the region of interest to a display.

In some embodiments, the method further comprises moving the transducerarray through the vascular pathway during the step of receiving soundwaves, the step of transmitting ultrasound signals, and the step ofreceiving ultrasound echo signals. The method may also comprise rotatingthe transducer array during the step of receiving sound waves, the stepof transmitting ultrasound signals, and the step of receiving ultrasoundecho signals. The transducer array may comprise two or more types oftransducer elements. The two or more transducer elements may comprise anultrasound transducer and a photoacoustic transducer.

Additional aspects, features, and advantages of the present disclosurewill become apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative embodiments of the present disclosure will be describedwith reference to the accompanying drawings, of which:

FIG. 1A is a diagrammatic schematic view of a medical sensing systemaccording to some embodiments of the present disclosure.

FIG. 1B is a diagrammatic schematic view of a medical sensing systemaccording to some embodiments of the present disclosure.

FIG. 2A is a diagrammatic schematic view of a medical sensing systemwith a sensor array according to an embodiment of the presentdisclosure.

FIG. 2B is a diagrammatic schematic view of a medical sensing systemwith a sensor array according to another embodiment of the presentdisclosure.

FIG. 2C is a diagrammatic schematic view of a medical sensing systemwith a sensor array according to another embodiment of the presentdisclosure.

FIG. 2D is a diagrammatic schematic view of a medical sensing systemwith a sensor array according to another embodiment of the presentdisclosure.

FIG. 2E is a diagrammatic schematic view of a medical sensing systemwith a sensor array according to another embodiment of the presentdisclosure.

FIG. 3 is a diagrammatic, perspective view of a vascular pathway andsurrounding tissue with an instrument positioned within the pathway andan external emitter according to an embodiment of the presentdisclosure.

FIG. 4 is a diagrammatic, perspective view of a vascular pathway andsurrounding tissue with an instrument engaged in mapping the vascularpathway.

FIG. 5 is a flow diagram of a method for mapping a vascular pathway witha transducer array according to some embodiments of the presentdisclosure.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of thepresent disclosure, reference will now be made to the embodimentsillustrated in the drawings, and specific language will be used todescribe the same. It is nevertheless understood that no limitation tothe scope of the disclosure is intended. Any alterations and furthermodifications to the described devices, systems, and methods, and anyfurther application of the principles of the present disclosure arefully contemplated and included within the present disclosure as wouldnormally occur to one skilled in the art to which the disclosurerelates. For example, while the intravascular sensing system isdescribed in terms of cardiovascular imaging, it is understood that itis not intended to be limited to this application. The system is equallywell suited to any application requiring imaging within a confinedcavity. In particular, it is fully contemplated that the features,components, and/or steps described with respect to one embodiment may becombined with the features, components, and/or steps described withrespect to other embodiments of the present disclosure. For the sake ofbrevity, however, the numerous iterations of these combinations will notbe described separately.

FIG. 1A is a diagrammatic schematic view of a medical sensing system 100according to some embodiments of the present disclosure. The medicalsensing system 100 includes a measurement apparatus 102 (such as acatheter, guide wire, or guide catheter). As used herein, “measurementapparatus” or “flexible measurement apparatus” includes at least anythin, long, flexible structure that can be inserted into the vasculatureof a patient. While the illustrated embodiments of the “measurementapparatus” of the present disclosure have a cylindrical profile with acircular cross-sectional profile that defines an outer diameter of theflexible measurement apparatus 102, in other instances, all or a portionof the flexible measurement apparatus 102 may have other geometriccross-sectional profiles (e.g., oval, rectangular, square, elliptical,etc.) or non-geometric cross-sectional profiles. Flexible measurementapparatus 102 may include, for example, guide wires, catheters, andguide catheters. In that regard, a catheter may or may not include alumen extending along all or a portion of its length for receivingand/or guiding other instruments. If the catheter includes a lumen, thelumen may be centered or offset with respect to the cross-sectionalprofile of the device.

The medical sensing system 100 may be utilized in a variety ofapplications and can be used to assess vessels and structures within aliving body. To do so, the measurement apparatus 102 is advanced into avessel 104. Vessel 104 represents fluid filled or surrounded structures,both natural and man-made, within a living body that may be imaged andcan include for example, but without limitation, structures such as:organs including the liver, heart, kidneys, as well as valves within theblood or other systems of the body. In addition to imaging naturalstructures, the images may also include man-made structures such as, butwithout limitation, heart valves, stents, shunts, filters and otherdevices positioned within the body. The measurement apparatus 102includes one or more sensors 106 disposed along the length of theapparatus 102 to collect diagnostic data regarding the vessel 104. Invarious embodiments, the one or more sensors 106 correspond to sensingmodalities such as IVUS imaging, pressure, flow, OCT imaging,transesophageal echocardiography, temperature, other suitablemodalities, and/or combinations thereof.

In the exemplary embodiment of FIG. 1A, the measurement apparatus 102includes a solid-state IVUS device, and the sensors 106 include one ormore IVUS ultrasound transducers and/or photoacoustic transducers andassociated control. As used herein, a “photoacoustic transducer”includes at least a sensor configured to detect photoacoustic wavesgenerated as a result of the interaction of optical pulses with tissue.In one embodiment, a photoacoustic transducer utilizes the sameultrasound detection mechanism as an IVUS ultrasound transducer. In someimplementations, a single transducer can serve as both an IVUStransducer and a photoacoustic transducer. In another embodiment, aphotoacoustic transducer uses a dedicated photoacoustic wave detectionmechanism distinct from that of an IVUS ultrasound transducer. Thesystem of FIG. 1A may include aspects of phased-array IVUS devices,systems, and methods associated with the Eagle Eye® Platinum catheteravailable from Volcano Corporation as well as those described in U.S.Pat. No. 7,846,101 and/or U.S. Pat. Application No. 14/812,792, filedJul. 29, 2015, each of which is hereby incorporated by reference in itsentirety.

The sensors 106 may be arranged around the circumference of themeasurement apparatus 102 and positioned to emit ultrasound energyradially 110 in order to obtain a cross-sectional representation of thevessel 104 and the surrounding anatomy. When the sensors 106 arepositioned near the area to be imaged, the control circuitry selects oneor more IVUS transducers to transmit an ultrasound pulse that isreflected by the vessel 104 and the surrounding structures. The controlcircuitry also selects one or more transducers to receive the ultrasoundecho signal. By stepping through sequences of transmit-receive sets, themedical sensing system 100 system can synthesize the effect of amechanically scanned transducer element without moving parts.

In one embodiment, the sensors 106 are disposed circumferentially arounda distal portion of the measurement apparatus 102. In anotherembodiment, the sensors 106 are contained within the body of themeasurement apparatus 102. In other embodiments, the sensors 106 aredisposed radially across the measurement apparatus 102, on a movabledrive member connected to the measurement apparatus 102, or on one ormore planar arrays connected to the measurement apparatus 102. Moreexamples of sensor placement are shown in FIGS. 2A-2E.

In some embodiments, the processing engine 134, which may be included inthe console 116, combines the imaging data acquired from both the IVUSand photoacoustic modalities into a single visualization. This use ofboth IVUS and photoacoustic modalities may provide a number ofadvantages over traditional systems using a single modality. First, theaddition of photoacoustic sensors may allow for higher resolutionmapping than traditional IVUS methods alone. Second, the combination ofIVUS and photoacoustic modalities may allow for faster imaging speedsthan OCT imaging or other methods. Third, the combination may allow fortwo-dimensional and/or three-dimensional imaging of the tissuesurrounding vascular pathways. Fourth, the use of photoacoustic imagingmay expand the diagnostic scope of an IVUS mapping procedure byincluding more of the surrounding tissue. In particular, the combinedIVUS and photoacoustic mapping can allow for detection of certain typesof cancers, tissue damage, and the mapping of multiple vascular pathwayswithout sacrificing the dependability of ultrasound in detectingplaques, stenosis, and other forms of vascular diseases. Fifth,combining these two modalities may allow substantial costs savingsbecause existing IVUS systems may be adapted to mapping systems usingboth modalities. Sixth, due to the interaction of optical pulses withtissue and the omni-directional emission of photoacoustic waves from thetissue, an optical pulse need not be emitted along the same axis as thetransducer. This allows for more flexibility in carrying out combinedphotoacoustic and IVUS procedures, and may allow for precise mappingprocedures even along deep or convoluted vascular pathways. Seventh, themapping capabilities of the present disclosure may be integrated withsome forms of laser therapy. For example, diagnosis of diseases intissue may be accomplished using the optical emitter in diagnostic mode.After a diagnosis, the optical emitter can be switched to a treatmentmode. In this regard, the map of the vasculature and surrounding tissuemay be used to guide the application of the treatment. After the opticaltreatment is finished, the optical emitter can be switched back todiagnostic mode to confirm treatment of the diseased portion of tissue.

Sensor data may be transmitted via a cable 112 to a Patient InterfaceModule (PIM) 114 and to console 116, as well as to the processing engine134 which may be disposed within the console 116. Data from the one ormore sensors 106 may be received by a processing engine 134 of theconsole 116. In other embodiments, the processing engine 134 isphysically separated from the measurement apparatus 102 but incommunication with the measurement apparatus (e.g., via wirelesscommunications). In some embodiments, the processing engine 134 isconfigured to control the sensors 106. Precise timing of thetransmission and reception of signals may be used to map vascularpathways 104 in procedures using both IVUS and photoacoustic modalities.In particular, some procedures may involve the activation of sensors 106to alternately transmit and receive signals. In systems using one ormore IVUS transducers that are configured to receive both photoacousticand ultrasound signals, the processing engine 134 may be configured tocontrol the state (e.g., send/receive) of one or more transducers duringthe mapping of the vascular pathway and surrounding tissue.

Moreover, in some embodiments, the processing engine 134, PIM 114, andconsole 116 are collocated and/or part of the same system, unit,chassis, or module. Together the processing engine 134, PIM 114, and/orconsole 116 assemble, process, and render the sensor data for display asan image on a display 118. For example, in various embodiments, theprocessing engine 134, PIM 114, and/or the console 116 generates controlsignals to configure the sensor 106, generates signals to activate thesensor 106, performs amplification, filtering, and/or aggregating ofsensor data, and formats the sensor data as an image for display. Theallocation of these tasks and others can be distributed in various waysbetween the processing engine 134, PIM 114, and the console 116.

Sill referring to FIG. 1A, a pullback device 138 may be connected to themeasurement apparatus 102. In some embodiments, the pullback device 138is configured to pull a measurement apparatus 102 through a vascularpathway 104. The pullback device 138 may be configured to pull themeasurement apparatus at one or more fixed velocities and/or fixeddistances. In other instances, the pullback device 138 may be configuredto pull the measurement apparatus at variable speeds and/or variabledistances. The pullback device 138 may be selectively connected to themeasurement apparatus 102 by mechanical connections such as male/femaleplug interactions, mechanical couplings, fasteners, and/or combinationsthereof. Further, in some instances the pullback device 138 may bemechanically coupled and/or integrated with the PIM 114. In suchinstances, connection of the measurement apparatus 102 to the PIM 114can couple the pullback device 138 to the measurement apparatus 102. Thepullback device 138 may be slid across a cable, track, wire, or ribbon.In some embodiments, the pullback device 138 is in communication withone or more of a processing engine 134, a PIM 114, or a console 116.Furthermore, the pullback device 138 may be controlled by signals sentthrough a processing engine 134, a PIM 114, or a console 116. Thepullback device 138 may also be placed in communication with anothermotivation device such as an actuator to drive an external opticalemitter. In some embodiments, an actuator is synched with the pullbackdevice 138 to synchronously move an external optical emitter and ameasurement apparatus 102.

In addition to various sensors 106, the measurement apparatus 102 mayinclude a guide wire exit port 120 as shown in FIG. 1A. The guide wireexit port 120 allows a guide wire 122 to be inserted towards the distalend in order to direct the member 102 through a vascular structure(i.e., the vessel) 104. Accordingly, in some instances the measurementapparatus 102 is a rapid-exchange catheter. Additionally or in thealternative, the measurement apparatus 102 can be advanced through thevessel 104 inside a guide catheter 124. In an embodiment, themeasurement apparatus 102 includes an inflatable balloon portion 126near the distal tip. The balloon portion 126 is open to a lumen thattravels along the length of the IVUS device and ends in an inflationport (not shown). The balloon 126 may be selectively inflated anddeflated via the inflation port. In other embodiments, the measurementapparatus 102 does not include balloon portion 126.

FIG. 1B is a schematic view of a system that includes an alternativemeasurement apparatus 102 according to some embodiments of the presentdisclosure. The measurement apparatus 102 of FIG. 1B is typical of arotational device such as a rotational IVUS ultrasound system and theone or more sensors 106 include one or more IVUS transducers arranged toemit ultrasound energy in a radial direction 110, as well as one or morephotoacoustic transducers. Again, a single transducer may serve as bothan IVUS transducer and a photoacoustic transducer. In such anembodiment, the one or more sensors 106 may be mechanically rotatedaround a longitudinal axis of the measurement apparatus 102 to obtain across-sectional representation of the vessel 104. The system of FIG. 1Bmay include aspects of rotational IVUS devices, systems, and methodsassociated with the Revolution® catheter available from VolcanoCorporation as well as those described in U.S. Pat. Nos. 5,243,988,5,546,948, and 8,104,479 and/or U.S. Pat. Application No. 14/837,829,filed Aug. 27, 2015, each of which is hereby incorporated by referencein its entirety.

The systems of the present disclosure may also include one or morefeatures described in U.S. Provisional pat. application Ser. Nos.62/315117, 62/315176, 62/315251, and 62/315275, each of which is filedon the same day herewith and incorporated by reference in its entirety.

FIGS. 2A-2E show examples of a sensor array 128 that may be used inconjunction with the measurement apparatus 102 according to someembodiments of the present disclosure. Only a portion of the measurementapparatus 102 is shown in FIGS. 2A-2E. In some embodiments, othercomponents are disposed distal or proximal to the sensor array 128 thatare not portrayed in FIGS. 2A-2E. In some embodiments, a sensor array128 is placed in a similar position as the sensors 106 of FIGS. 1A and1B. The sensor array 128 may include one or more sensors and emittersincluding ultrasound transducers, photoacoustic transceivers, opticalemitters, and/or optical receivers. In the example of FIGS. 2A-2D, thesensor array 128 is disposed around the circumference of the measurementapparatus 102, while in FIG. 2E, parts of the sensor array 128 aredisposed within the body of the measurement apparatus 102. Although notshown, sensor arrays 128 may also disposed on a distal end of themeasurement apparatus or on a drive member or other device separate fromthe measurement apparatus.

In the example of FIG. 2A, sensors of a first type 130 and sensors of asecond type 132 are included in a sensor array 128. The sensors of thefirst and second type 130, 132 may be disposed in alternating rows.These rows may be disposed radially and may extend part way orcompletely around the measurement apparatus 102. In some embodiments,rows of sensors placed in a staggered formation such that the ends ofindividual rows are not co-terminus. In some embodiments, rows ofsensors are placed adjacent to each other with no space in between.Alternatively, rows of sensors are spaced across the measurementapparatus 102 with space(s) therebetween. In some cases, 2, 3, 4, or 5rows of alternating sensors are disposed on the measurement apparatus102. As discussed above, the array 128 may be configured to rotatearound an axis of the measurement apparatus 102.

In the example of FIG. 2B, a sensor array 128 is shown with sensors of afirst type and a second type 130, 132 disposed in alternating columns.These columns of sensors may be disposed around the entire circumferenceof the measurement apparatus, or alternatively, may only reach aroundpart of the circumference. In some embodiments, columns of sensors areplaced adjacent to each other with no space in between. Alternatively,columns are spaced across the circumference of the measurement apparatus102 with space therebetween.

In the example of FIG. 2C, the sensors of the first and second types130, 132 are disposed on the array 128 in an alternating manner. In someembodiments, sensors of the first and second types 130, 132 are disposedon the array 128 in a checkerboard configuration such that individualsensors of the first type 130 are not adjacent to each other.Additionally, sensors of the first and second types 130, 132 may take uproughly equal proportions of the area of the array 128. Although theyappear as square or rectangular in the example of FIG. 2C, sensors ofthe first and second types 130, 132 may have circular, elliptical,polygonal, or other shapes. Sensors of the first and second types 130,132 may be spaced across the measurement apparatus 120 or they may beplaced flush against each other.

In the example of FIG. 2D, a sensor array 128 is shown with sensors ofthe first type 130 surrounded by sensors the second type 132. In someembodiments, the ratio of the surface areas of the sensors of the firstand second types 130, 132 on the sensor array 128 is 20% and 80%, 30%and 70%, or 40% and 60%, respectively. In one embodiment, sensors of thefirst and second types 130, 132 are disposed on the same layer and lieflush across the surface of the sensor array 128. In another embodiment,some sensors of the first and second types 130, 132 are raised relativeto other sensors. For example, sensors of the first and second types130, 132 may extend a distance of 0.25 mm, 0.5 mm, or 1 mm from the baseof the sensor array 128.

In the example of FIG. 2E, a sensor array 128 is shown with concentriclayers 136 of sensors. In some embodiments, layers 136 of sensors aredisposed coaxially with the measurement apparatus 102. Furthermore,sensors of the first and second types 130, 132 may form alternatinglayers 136 in the sensor array 128. For example, a sensor layer 136comprising ultrasound transducers may lie above a layer of photoacoustictransducers, which lies above another layer of ultrasound transducers.This arrangement may allow for a more compact measurement apparatus 102suitable for use within a wide range of vascular passages. Otherexemplary sensor arrays 128 and combinations of sensors are contemplatedbesides those shown in FIGS. 2A-2E. For example, a sensor array 128 maycombine the layers of FIG. 2E with the checkerboard layout of FIG. 2C tocreate a layered, alternating sensor array 128.

FIG. 3 is a diagrammatic, perspective view of a vascular pathway 104 andsurrounding tissue 210 with a measurement apparatus 102 such as thatdepicted in FIGS. 1A or 1B disposed within the vascular pathway 104. Anoptical emitter 220 is also shown emitting an optical pulse 230 towardan area of interest within the tissue. In some embodiments, the area ofinterest includes part of a vascular pathway 104 as well as adj acenttissue. In some embodiments, the optical emitter 220 is a laser sourcethat emits short laser pulses toward the area of interest. These laserpulses interact with the tissue 210 at a focus 242, generating a seriesof photoacoustic waves 240 that propagate through the tissue 210 and thevascular pathway 104. The photoacoustic waves 240 are received bysensors in a sensor array 128 connected to the measurement apparatus102. The sensor array 128 may be any of the exemplary sensor arrays 128of FIGS. 2A-2E. In some embodiments, the sensor array 128 is configuredto send and receive signals to image and/or map the vascular pathway.

An operator may move the measurement apparatus 102 through the vascularpathway 104 to image and/or map the vascular pathways 104. In somecases, the sensor array 128 is configured to image and/or map thevascular pathway 104 independently of the photoacoustic waves 240 bytransmitting ultrasound signals toward the vessel walls and receivingthe corresponding reflected ultrasound echo signals. This mappingfunctionality is explained further in conjunction with FIG. 4 .

In the example of FIG. 3 , the optical emitter 220 may be incommunication with a communication system 250 via connection 236. Insome embodiments, the communication system 250 is the processing engine134, the PIM 114, or the console 116 of FIG. 1A. The communicationsystem 250 may also be connected to the measurement apparatus 102 viaconnection 234. Furthermore, the measurement apparatus 102 may be indirect communication with the optical emitter 220 via connection 232. Insome embodiments, connections 232, 234, and 236 are cables capable oftransmitting electronic or optical signals. Furthermore, connection 232may be a microcable, connection 234 may be an optical fiber, andconnection 236 may be a wireless connection such as a Bluetooth or WiFiconnection. Additionally, the optical emitter 220 may include a wirelesssignal receiver. Connection 234 may also operate to power themeasurement device 102 including the sensor array 128.

The communication system 250 may coordinate the operation of the opticalemitter 220 and the sensors of the sensor array 128 by sending signalsto synchronize the emission of optical pulses 230 and the reception ofphotoacoustic signals by the sensor array 128. In some cases, thecommunication system 250 coordinates the operation of different sensortypes on the sensor array 128. In particular, the communication system250 may control the function of ultrasound transducers and photoacoustictransducers on the sensor array 128. The communication system 250 mayalso control one or more ultrasound transducers to function with bothultrasound and photoacoustic modalities. The operation of only one typeof sensor at a time may filter out noise and yield more accurate imagingand/or mapping of the vascular pathway.

FIG. 4 includes a depiction of a measurement apparatus 102. Themeasurement apparatus 102 may be a measurement apparatus 102 as depictedin any of FIGS. 1A, 1B, 2A-2E, or 3 . The measurement apparatus 102 maybe moved along direction 400 through a vascular pathway 104. In someembodiments, the measurement apparatus 102 is connected to and movedthrough the vascular pathway 104 by a pullback device 138 such as thatdepicted in FIGS. 1A and 1B. A sensor array 128 may be disposed on oraround the measurement apparatus 102. In some embodiments, the sensorarray 128 includes a plurality of ultrasound transducers which emitultrasound signals 402 radially toward a section 406 of the wall of thevascular pathway 104. The ultrasound signals 402 are reflected off thewall of the vascular pathway 104 and travel back toward the measurementapparatus 102 as ultrasound echo signals 404. These ultrasound echosignals 404 may be received by ultrasound transducers on the sensorarray 128. In some cases, a communication system 250 controls thetransducers of the sensor array 128 to emit ultrasound signals 402 andreceive ultrasound echo signals 404. In some embodiments, the medicalsensing system 100 is operable to image and/or map the vascular pathway104 by mapping sections 406 of the pathway wall as the measurementapparatus 102 is advanced through the vascular pathway 104 in direction400. In some embodiments, the sensor array 128 is operable to imageand/or map the vascular pathway 104 without rotating. In otherembodiments, the sensor array 128 is configured to rotate around themeasurement apparatus 102, as described in U.S. Provisional ApplicationNo. 62/315275 titled “ROTATIONAL INTRAVASCULAR DEVICES, SYSTEMS, ANDMETHODS UTILIZING PHOTOACOUSTIC AND ULTRASOUND TECHNIQUES,” which ishereby incorporated by reference in its entirety.

FIG. 5 is a flow chart showing a method 500 of mapping an area ofinterest using both photoacoustic and IVUS modalities. It is understoodthat additional steps can be provided before, during, and after thesteps of method 500, and that some of the steps described can bereplaced or eliminated for other embodiments of the method. Inparticular, steps 504, 506, 508, and 510 may be performed simultaneouslyor in various sequences as discussed below.

At step 502, the method 500 can include activating an external lasersource. This laser source may be the optical emitter 220 of FIGS. 3 and4 . In some cases, the external laser source is activated by acommunication system 250 by means of an electronic or optical signal.This signal may be sent wirelessly, and the external laser source may beequipped with a wireless signal receiver.

At step 504, the method 500 can include focusing a laser pulse on tissuein a region of interest having a measurement device with a sensor arrayincluding sensors of two or more types. In some embodiments, the regionof interest includes a portion of tissue including a portion of at leastone vascular pathway 104. The measurement device may be disposed withinthe vascular pathway 104. The region of interest may be chosen based ona suspected or diagnosed problem in the tissue, or based on theproximity of a region of tissue to problems within a vascular pathway104. In other embodiments, the region of interest is part of a moregeneral mapping plan. For example, a mapping plan for a section of avascular pathway 104 may involve the mapping of tissue surrounding thevascular pathway 104 along its length. The interaction of the emittedlaser pulse and tissue in the region of interest creates a number ofphotoacoustic waves 240 that emanate from the tissue.

In some embodiments, the measurement device is the measurement apparatus102 depicted in FIGS. 1A, 1B, 2A-2E, 3, and 4 . The sensor array may beany of the sensor arrays 128 depicted in FIGS. 2A-2E. In someembodiments, the sensors may be sensors 106 such as those depicted inFIGS. 1A, 1B, and 2-4 , and can include IVUS transducers, photoacoustictransducers, optical emitters, and optical receivers. In someembodiments, the sensor array does not rotate as it travels through thevascular pathway 104. In other embodiments, the sensor array rotatesaround a transverse axis of the measurement device. The sensor array maybe disposed on a revolving portion of the measurement device. In someembodiments, the sensors are disposed circumferentially around themeasurement device.

At step 506, the method 500 can include receiving sound waves generatedby the interaction of the laser pulse and tissue with the sensors. Insome cases, the sensors can function with the traditional IVUSfunctionality to receive ultrasound waves. In other cases, some or allof the sensors are dedicated to receive photoacoustic waves. In someembodiments, the sensors are controlled by a communication system 250like that depicted in FIGS. 3 and 4 . In another embodiment, aprocessing engine 134 or a PIM 114 may control the sensors on the sensorarray 128. Signals may be sent from processing engine 134 or the PIM 114to the sensors via connector 234, causing the sensors to receivediagnostic information such as sound waves, ultrasound signals, andultrasound echo signals.

At step 508, the method 500 can include transmitting ultrasound signalsinto the vascular pathway 104 with the sensors. Ultrasound signals maybe transmitted toward the walls of the vascular pathway 104 and may bedeflected off the walls of the vascular pathway 104 and propagatethrough the vascular pathway 104 as ultrasound echo signals.

At step 510, the method 500 can include receiving the ultrasound echosignals with the sensors. In some embodiments, the sensors may beoperable to receive sound waves as well as ultrasound signals. Thesensors of step 508 and the sensors of step 510 may be combined in asingle sensor, or alternatively, the sensors may be separate.

Steps 504, 506, 508, and 510 may be coordinated in the method 500 andoccur in various orders based on the desired outcome of a medicalprocedure. For example, transmission of ultrasound signals and receptionof ultrasound echo signals can occur at regular intervals throughout themethod 500, while reception of photoacoustic waves may occursporadically. This may be the case in a medical procedure to map avascular pathway 104 and spot-check trouble areas of tissue surroundingsections of the vascular pathway 104. Alternatively, steps 504, 506,508, and 510 are performed successively. For example, steps 506, 508,and 510 may be performed successively before proceeding to the next stepto avoid signal noise and allow for adequate signal processing whenmethod 500 is used in a system where a photoacoustic sensor and anultrasound transducer are each included in a transducer array.Furthermore, the steps of method 500 may be interleaved in variousorders.

At step 512, the method 500 can include producing an image of the regionof interest, including the vascular pathway 104 and surrounding tissue,based on the sound waves and the ultrasound echo signals. In someembodiments, a processing engine (such as the processing engine 134 ofFIG. 1A) in communication with the sensors produces the image of theregion of interest. This image can include both two-dimensional andthree-dimensional images based on the received sensor data. In somecases, the image includes a number of two-dimensional cross sections ofthe vascular pathway 104 and surrounding tissue.

At step 514, the method 500 can include outputting the image of theregion of interest to a display 118. This display 118 can include acomputer monitor, a screen on a patient interface module (PIM) 114 orconsole 116, or other suitable device for receiving and displayingimages.

In an exemplary embodiment within the scope of the present disclosure,the method 500 repeats after step 514, such that method flow goes backto step 504 and begins again. Iteration of the method 500 may beutilized to image and/or map a vascular pathway and surrounding tissue.

Persons skilled in the art will recognize that the apparatus, systems,and methods described above can be modified in various ways.Accordingly, persons of ordinary skill in the art will appreciate thatthe embodiments encompassed by the present disclosure are not limited tothe particular exemplary embodiments described above. In that regard,although illustrative embodiments have been shown and described, a widerange of modification, change, and substitution is contemplated in theforegoing disclosure. It is understood that such variations may be madeto the foregoing without departing from the scope of the presentdisclosure. Accordingly, it is appropriate that the appended claims beconstrued broadly and in a manner consistent with the presentdisclosure.

What is claimed is:
 1. An apparatus, comprising: an intravascularcatheter or guidewire configured to be placed within a vascular pathway,wherein the intravascular catheter or guidewire comprises a sensor arraycomprising at least one optical emitter and at least one transducer,wherein the sensor array is arranged in a first cylinder-shaped layerand a second cylinder-shaped layer, wherein the first cylinder-shapedlayer is positioned around the second cylinder-shaped layer, wherein theat least one optical emitter is configured to perform emission ofoptical pulses to tissue, wherein the transducer is configured toperform at least one of: reception of sound waves generated by thetissue as a result of interaction of the optical pulses with the tissue;transmission of ultrasound pulses; or reception of ultrasound echosignals associated with the ultrasound pulses.
 2. The apparatus of claim1, wherein the sensor array is further arranged in a thirdcylinder-shaped layer, wherein the second cylinder-shaped layer ispositioned around the third cylinder-shaped layer.
 3. The apparatus ofclaim 1, wherein the first cylinder-shaped layer and the secondcylinder-shaped layer are concentric.
 4. The apparatus of claim 1,wherein the first cylinder-shaped layer and the second cylinder-shapedlayer are coaxial with the intravascular catheter or guidewire.
 5. Theapparatus of claim 1, wherein the first cylinder-shaped layer ispositioned around a circumference of the intravascular catheter orguidewire.
 6. The apparatus of claim 5, wherein the secondcylinder-shaped layer is positioned within the intravascular catheter orguidewire.
 7. The apparatus of claim 1, wherein the at least onetransducer comprises: a photoacoustic transducer configured to performthe reception of the sound waves; and an ultrasound transducerconfigured to perform the transmission of ultrasound pulses and thereception of ultrasound echo signals .
 8. An apparatus, comprising: anintravascular catheter or guidewire configured to be placed within avascular pathway, wherein the intravascular catheter or guidewirecomprises a sensor array comprising at least one photoacoustictransducer and at least one ultrasound transducer, wherein the sensorarray is arranged in a first cylinder-shaped layer and a secondcylinder-shaped layer, wherein the first cylinder-shaped layer ispositioned around the second cylinder-shaped layer, wherein the at leastone photoacoustic transducer is configured to perform reception of soundwaves generated by tissue as a result of interaction of optical pulsesemitted by an optical emitter; and wherein the at least one ultrasoundtransducer is configured to perform: transmission of ultrasound pulses;and reception of ultrasound echo signals associated with the ultrasoundpulses.
 9. The apparatus of claim 8, wherein the first cylinder-shapedlayer comprises the at least one photoacoustic transducer and the atleast one ultrasound transducer, and wherein the second cylinder-shapedlayer comprises the at least one photoacoustic transducer and the atleast one ultrasound transducer.
 10. The apparatus of claim 8, whereinthe first cylinder-shaped layer comprises only the at least oneultrasound transducer, and wherein the second cylinder-shaped layercomprises only at least one photoacoustic transducer.
 11. The apparatusof claim 10, wherein the sensor array is further arranged in a thirdcylinder-shaped layer, wherein the second cylinder-shaped layer ispositioned around the third cylinder-shaped layer.
 12. The apparatus ofclaim 11, wherein the third cylinder-shaped layer comprises only the atleast one ultrasound transducer.
 13. The apparatus of claim 8, whereinthe first cylinder-shaped layer and the second cylinder-shaped layer areconcentric.
 14. The apparatus of claim 8, wherein the firstcylinder-shaped layer and the second cylinder-shaped layer are coaxialwith the intravascular catheter or guidewire.
 15. The apparatus of claim8, wherein the first cylinder-shaped layer is positioned around acircumference of the intravascular catheter or guidewire.
 16. Theapparatus of claim 15, wherein the second cylinder-shaped layer ispositioned within the intravascular catheter or guidewire.